1. Field of the Invention
The present invention pertains in particular (but not exclusively) to a so-called dual or multiple friction clutch device for installation in the drive train of a motor vehicle for the transfer of torque between a drive unit and a transmission, where the clutch device has a first friction clutch arrangement assigned to a first transmission input shaft and a second clutch arrangement assigned to a second transmission input shaft, and to a motor vehicle drive train equipped with this type of clutch device. With respect to the clutch device, the idea of the invention pertains primarily (but not exclusively) to so-called dual clutches of the friction disk type, for which it is known that an actuating device in the form of a hydraulic dual slave cylinder (xe2x80x9cdual CSCxe2x80x9d) can be provided for the optional actuation of the first and/or of the second friction clutch arrangement to engage or release the clutch.
2. Description of the Related Art
The general goal is to provide an actuating device which makes it possible to actuate the two clutch arrangements independently of each other without occupying a great deal of space in the drive train. The hydraulic dual CSC""s used up to now are quite compact, but they suffer from the disadvantage that pressurized hydraulic oil must be supplied to the transmission housing shroud, which can lead to problems associated with the leakage of oil. In particular, pulsating pressure loads on the seals lead to troublesome leaks, especially in the case of clutches of the so-called engaging type, that is, clutches of the NORMALLY OPEN type, upon which engaging forces must be exerted to engage the clutch.
Especially in the case of clutch arrangements of the NORMALLY OPEN type mentioned above, there is also the problem of how to absorb the axial forces which are produced in opposition to those exerted by the actuating arrangement and thus introduced into the clutch device. The absorption of these opposing forces by way of the power takeoff shaft (possibly the crankshaft) of the drive unit is problematic, because this can subject the bearings of the power takeoff shaft to excessive load. When conventional dual CSC""s are used, however, it has been found that it is relatively difficult in terms of the design engineering involved to absorb the opposing forces in any other way.
Against the background sketched above, the invention proposes an actuating device for a multiple friction clutch device installed in the drive train of a motor vehicle, possibly a dual friction clutch device, for introducing actuating forces, especially engaging or disengaging forces, into the friction clutch device in order to actuate, as desired, a first and/or a second friction clutch arrangement of the friction clutch device in the engaging or releasing direction. The actuating device comprises at least one first actuating element assigned to the first friction clutch arrangement and at least one second actuating element assigned to the second friction clutch arrangement, which actuating elements can be shifted axially relative to at least one support element, which is essentially fixed in the axial direction, to exert the actuating forces. Each of these actuating elements belongs to an actuator assigned to the clutch arrangement in question or can be shifted axially relative to the support element by the intermediate action of an actuator assigned to the associated clutch arrangement. According to the invention, the first and the second actuating elements engage with the support element such that a rotational movement of the actuating element relative to the nonrotatably supported support element, this movement being imparted by the intermediate action of the associated actuator, is converted into an axial translational movement of the actuating element relative to the axially supported support element.
It has been discovered, however, that the inventive idea is also advantageous in conjunction with xe2x80x9csingle clutch arrangementsxe2x80x9d, which have only one friction clutch arrangement. In accordance with a more general aspect, therefore, the invention proposes an actuating device for a friction clutch device installed in the drive train of a motor vehicle for introducing actuating forces, especially clutch-engaging or clutch-releasing forces, into the friction clutch device to actuate at least one friction clutch arrangement of the friction clutch device. At least one actuating element is assigned to the friction clutch arrangement or to a friction clutch arrangement, which element can be shifted axially relative to the minimum of one support element, which is essentially fixed in the axial direction, to exert the actuating forces. This actuating element belongs to an actuator assigned to the clutch arrangement or can be shifted axially relative to the support element by the intermediate action of an actuator assigned to the clutch arrangement. According to this more general aspect, the actuating element engages with the support element such that a rotational movement of the actuating element relative to the nonrotatably supported support element, this rotational movement being imparted by the intermediate action of the actuator, is converted to an axial translational movement of the actuating element relative to the axially supported support element.
The actuating device according to the invention can be produced compactly and at low cost. A high degree of functional (operational) reliability can also be achieved.
With respect to the way in which the actuating element or the actuating element in question engages with the support element, it is proposed that the engagement between the support element and the actuating element or between the support element and the first and/or the second actuating element be of the spindle or threaded type or that they engage with each other in the manner of a curve and its follower or of a ramp and a complementary ramp.
A preferred possibility is that one of the elements, i.e., either the support element or actuating element, have a single or double external thread extending around an outside circumferential surface with an essentially circular cylindrical shape, and that the other element have a single or double internal thread extending around an inside circumferential surface with an essentially circular cylindrical shape. The external thread and the internal thread are in direct, sliding engagement with each other or are in engagement with each other by the intermediate presence of at least one rolling or anti-friction element or of at least one sliding element. The internal thread and the external thread can be advantageously designed as flat threads, as trapezoidal threads, or as round threads. An embodiment with especially low friction is characterized in that the internal thread and the external thread cooperate with several balls serving as rolling or anti-friction elements and possibly with a ball return formed in the other element to form a ball screw. It is advantageous for the ball screw to be designed in accordance with U.S. published application no. 2002 074206.
An advantageous design variant is characterized in that one of the elements in question, i.e., either the support element or the (associated) actuating element, has a single or double external thread on an outside circumferential surface with an essentially circular cylindrical shape or a single or double internal thread on an inside circumferential surface with an essentially circular cylindrical shape. The other element has at least one thread engager supported axially on the first element, where the thread engager projects radially inward from an inner circumferential surface of the other element to engage in the external thread or projects radially outward from an outer circumferential surface to engage in the internal thread. The thread engager can be designed as a rolling or anti-friction element, for example, or as a sliding element. The thread engager is preferably guided with freedom of movement on the other element in an associated ring-shaped guide groove extending in the circumferential direction.
It is proposed as especially advantageous that the pitch of the external thread or the internal thread change in the axial direction. In this way, it is possible, for example, to obtain the desired relationship, such as a linear relationship, between the distance traveled by the actuator and the torque of the clutch, which is advantageous, for example, for the sake of good control performance (constant resolution). Nonlinear spring characteristics, such as the spring characteristics of the linings in particular, can be compensated by appropriately varying the pitch of the thread.
Another possibility for the engagement between the (associated) actuating element and the support element is to provide the support element and the (associated) actuating element with circumferential ramps, which rise axially in the circumferential direction; these ramps convert rotational movement into translational movement, possibly with the intermediate help of rolling elements. See, for example, DE 195 47 081 A1 and U.S. Pat. No. 5,141,091, the proposals of which can also be applied advantageously in conjunction with an actuating device according to the invention.
Another advantageous possibility is to provide one of the elements, i.e., either the support element or the (associated) actuating element, with at least one circumferential guide curve, which rises axially in the circumferential direction, whereas the other element has at least one curve follower, which is or can be brought into engagement with the guide curve, either directly or indirectly. This guide curve converts rotational movement into translational movement, possibly with the intermediate help of a plain bearing or an anti-friction bearing arrangement. The parts of an actuating element-support element arrangement of this type can be made of metal sheet or plate, for example, as a result of which manufacturing costs are significantly reduced.
The guide curve can rise axially in a linear manner in the circumferential direction. But is it also possible and advantageous for the guide curve to rise axially in a nonlinear manner in the circumferential direction, so as to obtain, for example, the desired relationship, especially an essentially linear relationship (see explanation above), between the distance traveled by the actuator and the torque of the clutch.
A preferred design of the actuating device is characterized in that at least one circumferential recess or opening defining the guide curve is provided in an outer circumferential surface and/or in an inner circumferential surface of the one element, which recess or opening serves as a link, in which the curve follower or an associated curve follower, designed as a link follower, can engage. It is not mandatory but preferred for the (associated) actuating element to have the guide curve or the link.
The support element and the actuating element or actuating elements can be designed as sleeves, possibly sleeves made of metal sheet or plate, which are coaxial to each other. The actuating element or at least one of the actuating elements can be formed by an outer sleeve, which extends radially around at least part of the outside surface of the support sleeve, which serves as the support element. In addition, the actuating element or at least one actuating element can be formed by an inner sleeve, where a support sleeve or the support sleeve which serves as the support element extends radially around at least part of the outside surface of the inside sleeve.
An especially advantageous embodiment of the actuating element but one which does not necessarily have to be used in conjunction with the design of the actuating element with a guide curve is characterized in that, as the support element, a radially outer support sleeve is provided on the outside and a radially inner support sleeve is provided on the inside, and in that the actuating element or at least one of the actuating elements is formed by an intermediate sleeve, which is installed radially between the outside support sleeve and the inside support sleeve. In reference to the design of an actuating device with a guide curve, the intermediate sleeve can be designed with at least one guide curve (preferably in the form of a link), which is or can be brought into engagement directly or indirectly with a curve follower extending radially between the outside support sleeve and the inside support sleeve. The follower can comprise a pin, which is attached to the outside support sleeve and/or to the inside support sleeve.
As previously mentioned, the support element and the actuating element or actuating elements can be designed as parts to be made of metal sheet or plate. This applies fundamentally to all of the design variants, but it is especially advisable for the design of the actuating device with at least one guide curve described above.
Another possibility is to design the support element and the actuating element or the actuating elements as plastic parts, where preferably one of the elements, i.e., the support element or the actuating element, or one of the elements of the support element plus actuating element pair in question is produced of a relatively flexible plastic, whereas the other element is made of a relatively rigid plastic. It can also be provided that one of the elements, i.e., the support element or the actuating element, or one of the elements of the support element plus actuating element pair in question, is made of metal, preferably of aluminum, whereas the other element is made of plastic.
With respect to the plastic material used, it is proposed that at least part of at least one or the other element be made of a lubricant-modified and/or self-lubricating plastic material. Friction-reducing materials which can be considered include, for example, PTFE in particular, but molybdenum phosphite and MOS2 are also suitable. Examples include the plastics polysulfone containing 15% PTFE and polyphthalamide containing 15% PTFE (PTFE=polytetrafluoroethylene). Insofar as combinations of a rigid and a flexible material are to be provided (which should be the goal), material pairings such as a thermoset plus aluminum and a thermoset plus thermoplastic can be considered.
A translational actuator can be assigned to the (or to each) actuating element, which actuator is or can be connected to the actuating element for motion in common by a coupling mechanism for converting translational movement into rotational movement. For this purpose, it is proposed in particular that the coupling mechanism comprise a traction and/or a thrust element, which can be driven by the actuator in a translational sense, which element acts on the actuating element or a lever section thereof, and which can pivot in a plane essentially orthogonal to the axis of rotation. This traction and/or thrust element is used to transfer an essentially tangential actuating force to the actuating element. The actuator can be, for example, an actuator based on the principle of a hydraulic slave cylinder.
Another advantageous possibility is a rotary actuator is assigned to the (or to each) actuating element, which actuator is or can be connected to the actuating element for motion in movement in common either directly or by the intermediate means of a coupling mechanism. It is possible, for example, to consider a rotary actuator based on an electric motor.
The rotary actuator can have an output section, which has an axis of rotation which is at least approximately parallel to the axis of rotation of the actuating element. It can be advantageous to provide a toothed wheel gearing system, by means of which the actuator and the actuating element are or can be connected to each other for motion in common. For example, the toothed wheel gearing system can have a toothed wheel on the actuator side as the input part and a toothed wheel or toothed wheel sector or toothed rim or toothed rim sector on the actuating element side as the output part, where the input part can simultaneously form the output part of the actuator and the output part can be designed as an integral part of or as a one-piece unit with the actuating element.
Another advantageous possibility is for the actuator to have an output section with an axis of rotation at least approximately orthogonal to the axis of rotation of the actuating element. It can be advantageous for the actuator and the actuating element to be connected or connectable to each other for motion in common by way of a worm gearing system. The worm gearing system can have a worm on the actuator side as the input section and a toothed wheel or toothed wheel sector or toothed rim or toothed rim sector on the actuating element side as the output section, where the input section can simultaneously form the output section of the actuator and the output section can be designed as an integral part of or as a one-piece unit with the actuating element.
Regardless of the way in which the actuator works and regardless of the means used to connect the actuator to the actuating element, it is also proposed as a further elaboration that an arresting device, possibly designed as a friction brake, be assigned to an output section or to the output section of the actuator and/or to a torque-transferring component of the connecting mechanism or of the transmission and/or to the actuating element. The arresting device is designed so that, regardless of the status of the actuation of the actuator at any one moment, the arresting device can preserve the instantaneous state of clutch actuation corresponding to the instantaneous axial and rotational position of the actuating element. As a result, the instantaneous state of clutch actuation can be preserved even if the current being supplied to the actuator, which is in the form of an electric motor, for example, is cut off. The arresting device can be activated and deactivated by means of, for example, an electromagnetic control element, which brings a friction brake into frictional engagement with an associated component or which releases this frictional engagement. The control element should be designed so that, when the current fails, the arresting function is necessarily activated or the existing state of activation is maintained.
It should also be remarked that the arresting function can also be an inherent property, so that there is no need for a separate arresting device. For example, a coupling mechanism such as a worm gearing system can be designed to be self-locking. In particular, it is possible for the frictional forces exerted by an arresting device designed as a friction brake to work together with inhibiting forces in the coupling mechanism and/or in the actuator to provide the previously described arresting function, that is, to hold the instantaneous state of clutch actuation independently of the instantaneous activation state of the actuator.
For the function of the actuating device, it is important for the support element to be secured against rotation. There are in principle many possible ways in which the support element can be secured in this way. The support element preferably has at least one rotational support section which is or can be brought into positive rotational support engagement with at least one assigned opposing rotational support section of a support base, which is stationary with respect to the clutch device, especially into engagement with the housing of the transmission of the drive train, in order to secure the support element against rotation. In addition, the support element can have at least one axial securing section, which is or can be brought into positive axial securing engagement with at least one assigned opposing axial securing section of a support base, which is stationary with respect to the clutch device, especially into engagement with the housing of the transmission of the drive train, in order to secure the support element in the drive train in the axial direction. In this context, it is especially preferred that the rotational support section and the opposing rotational support section simultaneously serve as the axial support section and as the opposing axial support section. An advantageous design is characterized in that the rotational support section and the opposing rotational support section can be brought into engagement in the manner of a quarter-turn fastener.
When the xe2x80x9caxial securingxe2x80x9d of the support element is mentioned above, it does not necessarily mean that the opposing axial forces which act on the support element during the clutch actuation process are absorbed via the axial securing section of the support base. It is preferable for these opposing axial forces to be absorbed in the clutch device, preferably in such a way that the opposing axial forces which develop in the clutch device and the opposing axial forces which develop in the actuating element cancel each other out, at least partially, preferably essentially completely, as will be explained in greater detail below.
It is advantageous for the actuating device according to the invention to have an actuating unit which can be handled as a single unit and which comprises at least one support element and the minimum of one actuating element.
In accordance with a second aspect, the invention pertains generally to an actuating unit for a friction clutch device installed in the drive train of a motor vehicle between a drive unit and a transmission for introducing actuating forces, especially clutch-engaging or clutch-releasing forces, into the friction clutch device to actuate at least one friction clutch arrangement of the friction clutch device for the purpose of engaging it or releasing it, together with an associated transmission-side mount. The actuating unit comprises at least one actuating element assigned to the friction clutch arrangement or a friction clutch arrangement, which actuating element can be shifted axially relative to at least one support element, which is essentially fixed in the axial direction, to exert the actuating forces. The actuating element belongs to an actuator assigned to the clutch arrangement or can be shifted axially relative to the support element by the intermediate action of an actuator assigned to the clutch device. The transmission-side mount provides a securing function for the actuating unit against rotation during the actuation of the clutch and, if desired (if provided), allows the actuating unit a certain freedom of axial movement relative to the transmission. The actuating unit being discussed can be an actuating unit according to the invention as described under the first aspect of the invention or a conventional actuating device. In the case of a single clutch, the conventional device could be based on a single hydraulic slave cylinder (single CSC), or, in the case of a dual clutch, it could be based on a dual hydraulic slave cylinder (dual CSC).
It is known that the side of the actuating unit facing the transmission can be mounted by means of a number of pins, such as three pins, which project axially from the transmission. These pins can allow the actuating unit to move to a certain limited extent in the axial direction relative to the transmission. If, during the actuation of the clutch, a reaction torque which tries to rotate the actuating unit is produced by the tangential actuation of a ramp engager or the like, or if a driving torque acting in the rotational direction is produced by the rotation of the clutch, these pins can absorb the reaction torque or the driving torque and thus prevent the actuating unit (which could possibly also be called an actuating module) from rotating relative to the transmission.
The conventional approach is disadvantageous to the extent that the pins can be subjected to very heavy loads under certain conditions. In addition, there is usually a relatively stiff connection between the actuating unit and the transmission and, via the actuating unit, between the transmission and the associated clutch device, as a result of which vibrations or stresses such as those which result from an axial offset between the drive unit (engine) and the transmission can occur in the actuating unit. This can cause the natural wobbling frequency of the overall arrangement to increase, which is usually undesirable.
A further disadvantage of the conventional solution is that, when the actuating unit is to be installed in the drive train, it often proves difficult to thread the actuating unit onto the transmission-side pins. Although it appears possible in principle to design the pins and the associated receiving holes in the actuating device with insertion bevels and/or with a comparatively large amount of clearance, this conceivable solution must usually be rejected in practice because it is necessary to ensure a certain minimum supporting length or load capacity, which would occupy too much space.
The task of the invention is to provide an actuating unit together with the transmission-side mount of the general type discussed above which avoids the problems or disadvantages associated with the conventional approach explained above or which at least significantly lessens their impact. To accomplish this task, the transmission-side mount has a mounting receptacle, which is or can be attached nonrotatably to the transmission, into which receptacle a plug-in section of the actuating unit, which is connected directly or indirectly to the support element or is an integral part thereof and the cross section of which is adapted to the shape of the mounting receptacle, is or can be inserted axially, where the mounting receptacle has at least one internal surface on which at least one external surface of the plug-in section can be secured directly or indirectly against rotation.
By providing a direct or indirect supporting engagement between the inside surface of the mounting receptacle and the outside surface of the plug-in section, the mount according to the invention, into which the plug-in section of the actuating unit is or can be inserted axially, makes it possible to secure the actuating unit against rotation relative to the transmission. If these surfaces are designed appropriately, they can absorb high overall supporting forces without the load per unit area being excessive at any one point. In principle, the actuating unit can be freely movable in the axial direction, so that the actuating unit, possibly together with an associated clutch module, can copy the axial movements which can result, for example, from the axial play of the crankshaft without the occurrence of undesirable axial loads on, for example, the crankshaft.
The actuating unit or actuating unit/mount combination according to the invention is especially useful for a friction clutch design of the NORMALLY OPEN type, but it can also be used advantageously in a friction clutch device of the NORMALLY CLOSED type.
It is advantageous to design the inside surface and the outside surface so that the actuating unit can be centered on the transmission by means of direct or indirect centering engagement between the inside surface and the outside surface.
An especially preferred embodiment is characterized by mating the inside surface and the outside surface to each other in such a way that the actuating unit retains some freedom of movement at least in the radial direction. As a result, an axial offset between, for example, the drive unit (engine) and the transmission can be absorbed without any stress, as explained above. In this relationship, but also in general, it is also proposed that the components be supported or the centering engagement accomplished by means of at least one elastic intermediate element. By means of the elastic intermediate element, the actuating unit can be pretensioned into a centering position defined by the transmission-side mount while compensating for axial offsets or the like at the same time.
For an especially reliable and easy-to-produce engagement between the mount and the actuating unit which also avoids high loads per unit area, it is proposed that the inside surface and the outside surface extend radially at least part of the way around the outside of an exit area for at least one transmission input shaft, preferably extending over a total circumferential angle of at least approximately 90xc2x0, more preferably of at least approximately 180xc2x0, and most preferably of at least approximately 270xc2x0. The inside surface and the outside surface should in this case proceed in the circumferential direction in such a way they provide support over the largest possible fraction of this angle, preferably over the entire circumferential angle, which therefore means that, to provide the means of preventing rotation, certain areas of the inside surface and of the outside surface will deviate from a circular cylindrical course relative to the axis of rotation. Ideally, the inside surface and the outside surface are designed in such a way that there is only one relative rotational position or one range of relative rotational positions between the mount and the actuating unit in which they can engage with each other.
So that the plug-in section of the actuating unit can be inserted easily into the transmission-side mount, at least a certain part of the inside surface of the transmission-side mount can be designed to serve as a threading-in surface, by means of which the axial movement of the actuating unit to be installed, which comes in contact with this surface, can be transformed into a radial movement of the actuating unit, which brings the actuating unit closer to the nominal radial position. The threading-in surface is preferably also designed to cooperate with the shape of the plug-in section in such a way that, to a certain extent, the axial movement of the actuating unit can be converted to a rotational movement, which brings the actuating unit closer to the nominal rotational position.
An effective embodiment is characterized in that the receptacle has at least one mount wall with the inside surface, which extends radially at least part of the way around the outside of an exit area or the exit area for at least one transmission input shaft. The plug-in section of the actuating unit can have at least one engagement area, which projects radially beyond the support element and which is preferably designed as a flange, on which the outside surface is formed. The transmission-side mount can be an integral part of the transmission housing and can be designed as, for example, an appropriate trough in the transmission housing or comprise at least one mount wall, constituting an integral part of the transmission housing and projecting from it. Preferably, however, the transmission-side mount is designed as a separate component or as a separate assembly, which is or can be attached permanently to the transmission so that it has no freedom of rotation and preferably also no freedom of axial movement.
In general, it is preferable for the mount to be designed as a one-piece, continuous part. It is effective to design the mount as a shell-like component. A mount of this type can be aptly called a xe2x80x9cmounting shellxe2x80x9d or xe2x80x9cmounting basketxe2x80x9d.
The plug-in section can be an integral part of the support element or form a single unit with it, but it is preferably a separate part or a separate assembly which is independent of the support element and which is or can be permanently attached to the support element so that it has no freedom of rotation and preferably also no freedom of axial movement.
It is advantageous for the actuating unit according to second aspect being discussed here to be designed in agreement with the above-discussed inventive proposals and inventive elaborations according to the first aspect of the invention. It is therefore possible for the actuating element and the support element to engage with each other in such a way that a rotational movement of the actuating unit relative to the nonrotatably supported support element, this rotational movement being imparted by the actuator, is converted to an axial translation of the actuating element relative to the axially supported support element.
The actuating unit can be provided for a single friction clutch device. In this case, the actuating unit will usually comprise precisely one actuating element. In addition, the actuating unit can be provided for a multiple friction clutch device, especially a dual friction clutch device, and thus makes it possible to actuate, as desired, the first or the second friction clutch arrangement of the friction clutch device in the engaging or releasing direction. For this purpose, the actuating unit can have at least one first actuating element assigned to the first friction clutch arrangement and at least one second actuating element assigned to the second friction clutch arrangement. These actuating elements can be shifted axially relative to the support element or to at least one support element, which is essentially fixed in the axial direction, to exert the actuating forces, where each of the actuating elements belongs to an actuator assigned to the associated clutch arrangement or can be shifted axially relative to the support element by the intermediate action of an actuator assigned to the clutch arrangement in question. In accordance with the first aspect of the invention, the first and second actuating elements engage the support element in such a way that a rotational movement of the actuating element relative to the nonrotatably supported support element, this rotational movement being imparted by the intermediate action of the associated actuator, is converted to an axial translational movement of the actuating element relative to the axially supported support element.
Further elaborative proposals can be derived from the proposals presented above for elaborations of the actuating device of the invention according to the first aspect of the invention.
The invention also pertains to an actuating unit for a combination according to the invention (actuating unit together with the transmission-side mount). Reference is made herewith to the features of the inventive combination according to the preceding explanations referring to the actuating unit.
The invention also pertains to a transmission-side mount for a combination according to the invention (actuating unit together with the transmission-side mount). Reference is herewith made to the features of the inventive combination according to the preceding explanations referred to the transmission-side mount.
The invention also pertains specifically to a clutch device, possibly to a dual or multi-clutch device, for installation in a motor vehicle drive train between a drive unit and a transmission. The clutch device includes a housing arrangement, which is or can be connected to a drive element for rotation in common around an axis of rotation; at least one clutch arrangement, assigned to a transmission input shaft, this clutch arrangement having at least one pressure plate, by means of which at least one friction area of at least one clutch disk can be pressed against an opposing support area, which can rotate along with the housing arrangement; an actuating arrangement for engaging and releasing the clutch arrangement by the intermediate action of an actuating element of the actuating arrangement assigned to the clutch arrangement, which actuating element can be shifted axially relative to at least one support element of the actuating arrangement, the support element being essentially fixed in the axial direction, where the actuating element belongs to an actuator assigned to the clutch arrangement or can be shifted axially relative to the support element by the intermediate action of an actuator assigned to the clutch arrangement. According to the invention, it is proposed that the actuating arrangement comprise an actuating device or an actuating unit according to the invention which includes the actuating element and the support element, possibly together with the associated transmission-side mount, as described above.
In the conventional case, the opposing axial forces resulting from the axial displacement of the actuating element relative to the support element and the opposing forces resulting from the transfer of the axial control and/or positioning forces are supported independently of each other. According to the conventional approach, for example, a clutch-release bearing arrangement and its associated actuator (such as a hydraulic slave cylinder) are supported axially on the transmission, whereas the clutch device is supported on the power takeoff shaft (especially the crankshaft). When a hydraulic slave cylinder is being used as the actuator, it is possible to interpret the piston element and the associated clutch-release or clutch-engaging bearing as the actuating element and the cylinder body defining the cylindrical space as the support element.
In conjunction with so-called multi-clutch devices, especially dual clutch devices with several clutch arrangements, it appears advantageous to depart from the xe2x80x9cNORMALLY CLOSEDxe2x80x9d design, which so far has been the dominant design for clutches of the friction disk type, and to adopt the xe2x80x9cNORMALLY OPENxe2x80x9d design. This means that, while the vehicle is being driven, axial clutch-engaging forces must be absorbed continuously. If this axial support occurs directly or indirectly via the power takeoff shaft of the drive unit, the bearings of the power takeoff shaft could be subjected to excessive load over the long term.
In contrast, especially for the design of the clutch device with at least one clutch arrangement of the NORMALLY OPEN type, but also for a design of the clutch device with at least one clutch arrangement of the NORMALLY CLOSED type, the axial control and/or positioning forces exerted by the actuating element in correspondence with its axial position are transferred to the pressure plate and/or to a spring arrangement assigned to the pressure plate. The opposing axial forces induced during the axial shift of the actuating element relative to the support element and/or during the buildup of the axial control and/or positioning forces are absorbed by way of the support element; and the opposing axial forces induced by the transferred axial control and/or positioning forces are absorbed by the housing arrangement. The support element and the housing arrangement are supported axially with respect to each other in such a way that the opposing axial forces are absorbed by the housing arrangement and the opposing axial forces are absorbed by the support element cancel each other out at least partially and preferably cancel each other out almost completely. According to the invention, the opposing axial forces cited above cancel each other out at least partially, so that the power takeoff shaft is subjected at most to only light axial loads. Ideally, the axial support relationship between the support element and the housing is such that a closed circuit is obtained for the flow of axial forces within the clutch device.
An advantageous embodiment is characterized in that a pivot bearing arrangement is provided between a preferably cover-like section of the housing arrangement and the support element, possibly designed in the form of a sleeve, to transfer axial forces between the cover section of the housing and the support element. The actuating arrangement can have an actuating lever arrangement or an actuating spring arrangement assigned to the pressure plate, this lever or spring arrangement possibly being attached to the housing section. It is proposed as an elaboration that a support area which rotates in common with the housing arrangement be assigned to the actuating lever or actuating spring arrangement, on which support area the actuating lever or actuating spring arrangement is or can be axially supported directly or indirectly.
It is advantageous for the housing arrangement, the minimum of one clutch arrangement, and the actuating arrangement to form a single installation unit.
The invention also pertains to a clutch device, possibly a dual clutch or multi-clutch device, for installation in a motor vehicle drive train between a drive unit and a transmission, comprising at least one multi-disk clutch arrangement, which is assigned to a transmission input shaft and is provided for operation by the action of a operating fluid, especially a cooling oil, and an actuating device or actuating unit, which is or can be brought into working connection with the clutch arrangement and which, if desired, can be integrated into the clutch device, for engaging and releasing the clutch arrangement by the intermediate action of an actuating element of the actuating device or actuating unit assigned to the clutch arrangement. The actuating element can be shifted axially relative to at least one support element, essentially fixed in the axial direction, of the actuating device or actuating unit, and belongs to an actuator assigned to the clutch arrangement or can be shifted axially relative to the support element by the intermediate action of an actuator assigned to the clutch arrangement. The actuating device or actuating unit in question is an actuating device or actuating unit according to the invention, possibly with the associated transmission-side mount described above.
An especially preferred embodiment of the clutch device is characterized in that operating fluid can be supplied or, during operation, forcibly supplied at least to the areas where the support element and the (associated) actuating element engage with each other, by which mutual engagement the rotational movement is converted to the translational movement, the effect thus being to provide these engaging areas with wet lubrication. This wet lubrication makes it possible to reduce friction to an especially low level.
The clutch devices discussed above can be a multi-clutch device or a dual clutch device, each of which has a first clutch arrangement assigned to a first transmission input shaft and a second clutch arrangement assigned to a second transmission input shaft. Depending on the type of clutch, the clutch arrangement in question is, for example, a clutch arrangement of the friction disk type or a clutch arrangement of the multi-disk type.
The invention also pertains to a motor vehicle drive train with a clutch device installed between a drive unit and a transmission, which clutch device has an actuating device or actuating unit according to the invention (possibly with the associated transmission-side mount) or to which is assigned an actuating device or actuating unit according to the invention (possibly with the associated transmission-side mount). The invention is particularly concerned with the clutch devices according to the invention discussed above.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.